Foldable stressed skin structure



May 13, 1969 c. w, WlLLlAMS, JR v FOLDABLE STRESSED SKIN STRUCTURE Original Filed Dec. 21, 1964 Sheet -01 s INVENTOR.

df/orweg rMaxy 13, 1969' c. w. WILLIAMS, JR 3,443,344

- FOLDABLE STRESSED SKIN STRUCTURE Original Filed Dec. 21, 1964 Sheet 3 of 3 M167 g J yf c. w. WILLIAMS, JR 33435344 FOLDABLE STRESSED SKIN STRUCTURE Original Filed Dec. 21, 1964 Sheet 3 INVENTOR.

United States Patent 0 US. C]. 52-18 13 Claims ABSTRACT OF THE DISCLOSURE A three-dimensional foldable structure having continuously joined elements with parallel fold lines which are non-linear to a first degree when in a collapsed condition and in which a change in the degree of non-linearity of the fold lines occurs when the volume enclosed by the structure is increased.

BACKGROUND OF THE INVENTION This is a continuation of my copending application Ser. No. 419,984, filed Dec. 21, 1964 and now abandoned.

The invention is particularly adapted to the construction of enclosures or buildings which are readily transportable from a fabrication site to an erection site where the degree of collapse is altered to produce a configuration for coverage'of large areas by a relatively thin self-supporting skin.

In providing coverage for large floor areas either as a temporary measure or for permanent use, the requirement for many trades and skills at erection sites leads to high unit cost. Many different approaches have been tried in prefabrication of building structures to minimize the construction site effort. The present invention is directed to a building system in which a relatively thin skin is provided in such a manner as to be self-supporting, but which is prefabricated for transport to a construction site at which location the erection effort is minimal.

SUMMARY OF THE DISCLOSURE Elements of a web of any material and of any dimensions are constructed of straight or curved segments which enclose given angles. The segments may be similar on each side of the enclosed angles, and the elements so constructed must be interconnected so that each element will have a variable depth dimension, which is the dimension from the upper marginal edge to the lower marginal edge of the element, projected upon the plane of maximum depth. A structure made up of such elements reacts to change the given angles enclosed within the segments when the depth dimension of the structure is changed as the structure is expanded from its folded condition, the plane of each element in the folded condition serving to define its plane of maximum depth.

The invention makes possible the construction of a number of devices useful in the sciences, in the chemical industry, in the construction industry, in advertising, in toy manufacture, and many other fields.

An example of the invention is a collapsible and easily transportable building made of a stressed skin of wood or of metal. The method of the invention permits determination of the proper shapes of the wood sections WhlCh will make a predetermined shape of the building when the wood sections, joined together, are expanded.

More particularly, in accordance with the invention, there is provided a structure forming unit which is collapsed as in an accordion-pleated skin in which the folds of adjacent portions, or elements, extend parallel one to the other, continuously along the arch formed by the unit but the portions themselves are normally non-linear to a first degree; that is, the elements themselves are generally in an arched configuration. The non-linearity of the portions is changed in degree as the structure is unfolded. Preferably, a foundation supports and/or anchors the opposite ends of the folded portions when unfolded.

In one embodiment the unit includes a plurality of planar elements with arched non-linear upper and lower marginal edges. Each element is secured along one marginal edge to the corresponding edge of the element next adjacent thereto on one side and secured along the other marginal edge to the corresponding marginal edge of the next adjacent element on the other side. The pleats thus formed may be unfolded by exerting oppositely directed forces to the end elements of the stack normal to the plane of the end elements when folded. The stack of pleated elements, when unfolded, forms an expanded three-dimensional structure which is pre-stressed and self-supporting.

In one embodiment, the invention involves constructing a structural module of a plurality of curved elements, or panels, of a web of any material and where the elements have any dimensions. The elements are interconnected so as to form a series of continuous pleats. Imposed is the condition that the elements must have a variable depth. The variation in depth of a curved element may be defined as the shortest distance from a line joining adjacent peaks of the pleated construction to the valley formed by the fold line between the two peaks. Alternatively, this variation in depth may be defined as the difference between the outside radius and the inside radius of a uniform are at any point on the projection of the element on a plane established by the maximum depth of the element; this difference is the distance between the upper and lower marginal fold lines of the projected element. When the pleated structure is partially unfolded to increase the length of the structure, the depth of the pleats as defined above will change from the initial value when the structure is folded to some lesser depth. When this occurs, then the angle included between radii to any two fixed points on any uniform are of the element, as projected on said plane of maximum depth, will be caused to change so that as the depth changes the angle is caused to change in generally inverse proportion. Viewed another way, the angle included between lines tangent to said two fixed points on any uniform arc of the element, as projected on said plane of maximum depth, will be caused to change so that as the depth of the pleats changes, the angle included between the tangent lines changes approximately in direct proportion. Where the element is constructed of straight line segments, this latter function i.e., a decrease in angle with expansion of the pleats, will be true for the angle included between said straight line segments. Thus, partial expansion of the folded structure will cause an increase in the height of the arched or curved elements while decreasing the span thereof.

3 BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is an end view of one form of a pleated unit;

FIGURE 2 is an end view of the unit of FIGURE 1;

FIGURE 3 is an isometric view of the unit of FIG- URES 1 and 2 unfolded;

FIGURE 4 is an end view of the enclosure of FIG- URE 3;

FIGURE 5 is a sectional view taken along the lines 55 of FIGURE 3;

FIGURE 6 illustrates a modification of the invention;

FIGURE 7 illustrates an embodiment of the invention designed to form an arch structure;

FIGURE 8 is a plan view of the elements of a third modification of the invention;

FIGURE 9 is a side view of the top and side portion of FIGURE 8 joined together and pleated;

FIGURE 10 is a sectional view taken along the lines 1010 of FIGURE 9;

FIGURE 11 is a side view of the building when erected;

FIGURE 12 is a view taken along lines 1212 of FIGURE 11;

FIGURE 13 is a side view of the pleated end panel; and

FIGURE 14 is an end view of the building of FIGURE 11 with the end panel in place.

DESCRIPTION OF PREFERRED EMBODIMENTS While there are a number of different specific embodiments in which the present invention may be incorporated and used to advantage, three examples will be presented herein as representative of the present invention and will include the significant features thereof with the understanding that modifications may be employed which involve the invention in forms different than those specifically described.

FIGURES 1-5 illustrate a first embodiment of the invention. In FIGURE 1 there is illustrated a side view of a stack 8 of structural elements 10 arranged in arched relation. Each element includes four linear sections angularly disposed one with another and arranged in arched relation to cover a span reaching from point 6 at one end of the element to point 7 at the other end of the element. The arch so formed has a height H which is the distance between a line drawn from point 6 to point 7 and the inside peak edge of the element. The end section 11 is relatively short, has parallel marginal edges and extends to a center section 12 with an angle 0 between the marginal edges thereof. The center section 12 extends from section 11 to center section 13 with a different angle 1;!) formed between the adjacent edges of sections 12 and 13. The center section 13 extends to an end section 14 which is identical to end section 11 with the angle 0 formed between the edges of sections 13 and 14. Sections 11 and 14 are mirror images of each other as are sections 12 and 13. While the separate sections 11-14 have been referred to, they may be separate areas of a single sheet of material, as for example N0. 24 gauge galvanized steel.

A plurality of such elements are joined together to form the stack 8 for the construction of a corrugated enclosure, an enclosure having a gabled-roof and vertical side walls all of which are pleated, or corrugated. As illustrated in FIGURE 2, a plurality of elements are joined together to form a folded compact structural unit. Each of the elements 10, 15, 16, 17-18, are joined together along the marginal edges thereof in the following manner. The lower margin of the adjacent elements, or panels, 10 and are joined together along the entire length thereof as at line 21 (FIGURE 3) to form a fold line which in this case is a valley in the pleated structure. In a similar manner, the upper margin of adjacent panels 15 and 16 are joined along the entire length thereof to form fold line 22 which, in this case, is a peak in the pleated construction of the present invention. Likewise, panels 16 and 17 are joined together along the lower marginal line 23. By securing each of the panel elements 10-18, as by fastening one marginal edge of each panel to the corresponding marginal edge of the panel located on one side and along the other marginal edge to the panel on the other side, a pleated stack of elements may thus be formed which can be shipped from a point of fabrication in compact folded form. They may then be expanded or unfolded to form a suitable enclosure as shown in FIGURE 3. The stack of FIGURE 2 is illustrated in FIGURE 3 in an expanded state wherein there is provided a corrugated gabled-roof, stressed skin, self-supporting building. The panel 10 is located at the far end of the building and the panels 15, 16 and 17 are located successively along the length of the building with the common margins, or boundaries between adjacent panels joined to form connecting zones, or fold lines.

A comparison of the configuration of element 10 i1- lustrated in FIGURE 1 with its configuration in the expanded structure of FIGURE 3 indicates the degree of change imposed on each element of the stressed skin as the structure is expanded from its initial stacked condition. Thus, the unfolding of the pleats forces the elements out of the generally planar form of FIGURES 1 and 2 into the three-dimensional form of FIGURE 3, and the stresses generated during such expansion cause the angles enclosed by the various sections of each element to change. The end sections 11 and 14 of element 10 are forced into the vertical position of side walls 26 and 27, as shown in FIGURES 3 and 4, and the center sections 12 and 13 are caused to bend with respect to each other, as a comparison between FIGURES 1 and 4 will illustrate. These changes reduce the span of element 10 and increase its height, while the length of the structure increases. This length is the distance between edge 20 of element 10 and edge 19 of element 18. Considering the plane defined by element 10 in FIGURE 1 to be the reference plane for that element, and projecting all angles onto that plane (the plane of the sheet of drawings) it will be seen that the angles 0 and between adjacent sections of element 10 have been changed to angles 0 and 15 in the expanded configuration of FIGURE 4. In a similar manner, each of the remaining elements 15 through 18 are distorted by the expansion of the structure so that their corresponding enclosed angles are similarly changed in their individual planes of projection.

In comparing the angles 0 and 11 before and after expansion of the pleated stack of elements, it will be seen that angle 6 is substantially greater than angle 0. In the specific embodiments of FIGURES 1 to 4, the angle 0 is about 160, while angle 0' is about 104. Similarly, angle which is about 174 in FIGURE 1, decreases upon unfolding of the structure to about at angle in FIG- URE 4. Again, the angles noted above are measured at the reference plane of element 10, onto which these angles are projected.

As the pleated stack of elements shown in FIGURE 2 is expanded to form the structure of FIGURE 3, each of the elements will tilt out of its initial plane of reference and become nonplanar; that is, the stresses caused by the rotation of each element out of its reference plane while it is fastened to another (adjacent) element, which is also being rotated out of its reference plane in the opposite direction, causes the element to be deformed at the junctions of the several sections and to become non-planar at these points. It is this deformation in the plane of the element itself which causes the side walls 26 and 27 to be formed as the structure is expanded. Each of elements 10 and 18 is similarly deformed to provide the gabled roof, vertical wall structure of FIGURES 3 and 4.

FIGURE 5 illustrates a partial sectional view of the expanded stack of elements taken along lines 5-5 of FIGURE 3, showing the angle A to which the panels are extended. In FIGURE 5, the angle A is about 156; the corresponding angle of the folded stack in FIGURE 2 is Thus, the folded stack, the elements of which were initially parallel to the plane of element 10, indicated in FIGURE as reference plane 40, is stretched from the configuration of FIGURE 2 to that of FIGURE 3, while each element rotates out of its reference plane by an angle [3. The panels of the pleated structure are so stressed that the projections of the marginal edges of each panel onto their respective reference planes, which edges are nonlinear to a first degree as represented by angles 0 and 15, are distorted so that they become non-linear to a second degree, as represented by angles 0' and After the structure has been unfolded to the form illustrated in FIGURE 3, the lower ends 30 and 31 may be secured to a suitable foundation 32, whereby the structure will be anchored and will support itself and will withstand reasonable wind and snow loading.

In the foregoing discussion, it has been indicated that the margins 21-23 were continuously joined. If the material adjacent to a weld zone at the margins is relatively light and resilient, the sharply angular structure illustrated in FIGURE 5 would not be precisely achieved. Rather the panels will be forced into -a slight curvature adjacent each of the boundaries, the curvature being generally S shaped.

In FIGURE 6, the curvature which would result is illustrated in somewhat exaggerated form. FIGURE 6 also shows a modified form of joint which may be employed to join the panels. In this case, lines of bolts or rivets 55 and 56 are employed adjacent the margins to be joined. The lower edges of the margins of panels 10 and are joined by a line of rivets 55. The upper margin of panels 15 and 16 are joined by a line of rivets 56. If desired, the rivets 55 and 56 may be located substantially inwardly of the margins and the margins then rolled over to aid in weather-proofing.

In FIGURE 7, there is illustrated a development of a self-supporting stressed skin arch wherein the structural features are generally of a type above described in connection with FIGURES 16. Whereas each element, or panel, of the structure of FIGURE 1 may be considered as an arch formed by a plurality of straight sections (in this case, four sections), the segments might be so numerous that each included angle 0 would approach 180 so as to form a curved arch such as that shown in FIG- URE 7. Thus, in this embodiment a set of curved panels such as the panel 60 are secured together at opposite marginal edges as generally above described. The stack 61 of panels is folded into a compact assembly suitable for transport, with each element of the stack being substantially parallel to the plane of reference of element 60. This plane of reference is also indicated at line 65, adjacent the cross-sectional view of stack 61. Reference plane 65 is the plane of maximum element depth for element 60, with points 68 and 70 on the plane indicating the projected outside radius and inside radius, respectively, of the element 60. The vertical distance between points 68 and 70, or the difference between the radii to these points, is the depth of element 60. The plane of reference of an element will generally pass through one of its fold lines. As the stack 61 is expanded, the configuration of the panel 60, as projected on the reference plane, is modified, with the projected image having an increasing curvature, as illustrated by the configuration 60a, as the stack 61 is expanded to the degree illustrated by the section 61a. Note that the depth of the element 60 decreases as the stack expands, and points 68' and 70' move closer together on plane 65. As the stack is further expanded to the configuration 62a, the panels then assume a semi-circular form as illustrated by the configuration 6012, with the projected depth of the element at a value much less than that of 61a as indicated by points 68" and 70". The distance between these points not only is a measure of the depth of the element on the reference plane, but is a measure of the depth of the pleats of the present structure. Note that the apparent increased curvature of the inside marginal edge of element 60- is in the reference plane. The interconnection of the elements making up the pleated stack generates stresses as the structure is expanded to deform the element 60 out of its original plane so that it becomes non-planar and thus curves downwardly as shown in FIGURE 7. Each element in the stack similarly becomes non-planar, with respect to its own original plane, and becomes non-linear to a second degree as projected on its reference plane as the stack is expanded. Thus, the height of the arch increases as its span decreases. If tangent lines were drawn to fixed points on the projected image of arched element 60, it would be seen that the angle enclosed between such tangent lines would decrease as the stack is expanded and the depth of the pleats decreases.

The fundamental concept involved can be employed for various specific applications. For example, the panel 60 may be 60 feet in length with the margin edges cut on radii of about feet and with the depth of the panels in the order of 3 feet. A pleated arch may be formed therefrom having a 50 foot span and a 15 foot ceiling, or height, having pleats about one foot deep, and an arch radius of about 30 feet encompassing an angle of about 121.

The foregoing embodiments of the invention represent construction in which generally unitary, elongated panels are joined together at opposite margins to form a stacked construction module. In FIGURES 8-14 the roof portion is formed from a single panel 100. One side wall is formed by a second panel 101. The other side wall is formed by a third panel 102. The edges 103 and 104 of panels 101 and 102 are serrated. The side wall panels 101 and 102 are the same length as the roof panel 100. In fabrication, the side panel 101 may be turned over onto the roof panel as indicated by the dotted outline of panel 101. In this position, the serrated edge 103' is joined to the surface of the roof panel 100 near margin 105. In a similar manner, the serrated edge 104 of the panel 102 is joined to the same surface of the roof panel 101 but near the opposite marginal edge 106.

With the side walls thus secured to the roof panel, they may then be folded outwardly from the roof panel to force the roof panel as well as the side wall panels into a corrugated configuration. More particularly, as the side wall panels are bent outwardly to the configuration illustrated in FIGURE 9, the side wall panels, as well as the roof panel, will have the configuration shown in FIGURE 10. That is, the originally plane surfaces are forced into relatively tight folds forming, in effect, joined elements such as those illustrated in FIGURE 1, so that the wall panels and the roof panel are compacted into a relatively short module. As shown in FIGURE 9, the folded wall panels 101 and 102 form angles 7 with the folded roof panel 100, the plane of FIGURE 9 being the reference plane.

In the configuration illustrated in FIGURE 9, the roof and side panels may then be transported to an erection site. As the corrugations are expanded to form a roof surface 110, FIGURE 11, the side wall panels will be forced to assume a vertical orientation, that is, angles 7 will be forced to change to angles 7' in the manner of the embodiments described above. The side wall panels will be corrugated to the same degree as the roof panel with the valleys of the side walls being connected to the roof valleys, and the corresponding peaks being connected. A view taken along line 1212 of FIGURE 11 of the structure thus formed is illustrated in FIGURE 12. The edges 105 and 106 of the roof panel 100 extend slightly beyond the margins of the side panels 101 and 102, respectively.

Two end panels 120 and 121 are provided for this structure to form end closures for the structure of FIG- URE 12. The and panels are shown as secured in place in FIGURE 11. As illustrated in FIGURE 8, the end panels have notches 123 near the marginal edges thereof. They are then folded as along lines 122 and 126 to form the stacked structure of FIGURE 13. When expanded, the end panels are of the configuration shown in FIGURE 14. The edges of the notches 123 are then welded or other- WiSe secured together so that as the end panels are unfolded and secured along line 124 to the ends of roof panel 100 and to the ends of the side wall panels 101 and 102, the end wall will likewise be corrugated in generally the same configuration as the side walls and the roof and with the fold lines 126 thereof lying in the plane 125, FIG- URE 11. Thus, the enclosure illustrated in FIGURE 14 is a five-sided structure which may be supported on a suitable foundation 130 with the bottoms of the side walls and of the end walls embedded therein or secured thereto to provide stability to the entire structure.

Structures formed in accordance with the present invention may be fabricated other than at the erection site. A structure formed as in FIGURES 1 and 2, when taken to the site of erection, may be supported on a temporary scaffold having tracks or slide ways 150 and 151. The ways 150 and 151 preferably extend at least the length of the structure to be formed. The folded structure may then be changed into its final form, shown in FIGURE 3, 'by applying forces as indicated by arrows 152 and 153, FIGURE 2. The supports 150 and 151 will be positioned as to accommodate the change in attitude of the elements of the folded structure, as it is expanded into the form shown in FIGURE 3. Similar support means may be provided for the structures shown in FIGURES 7, 9 and 12. After the structure is expanded to its final form and suitably anchored, the temporary supports 150 and 151 are removed, leaving the building interior unobstructed. Thus, in accordance with the invention, a web is formed of material having non-linear parallel fold zones which may be folds in a large web, or connecting lines between marginal edges of adjacent individual panels. These fold zones have a first degree of non-linearity in a reference plane, which degree is then altered in the reference plane as the structure is expanded to change the volume encompassed by the web. This expansion changes the amount of fold in the fold zones, as illustrated in FIGURE 7. In its changed condition, the structure is anchored to provide a self-supporting expanded framework.

In connection with the foregoing description, the fold lines have been described as being parallel. In FIGURE 2, it will be seen that the planes in which the fold lines occur are precisely parallel. In the expanded form, as shown in FIGURE 3, the same fold lines are still in planes which are parallel and thus the fold lines may be termed parallel. This will be true even though the lateral dimensions of the segments 11, 12, 13 and 14 of FIGURE 1 may vary. The same is true of the system shown in FIGURE 7. The two arcs forming the inner and outer boundaries of the element 60 may be of different radii so that, in the form 60b of FIGURE 7, the curvature would not be cylindrical but would exhibit compound curvature. Further, it may be possible that in FIGURE 3, the forces applied to the skin structure are such that the fold planes would not all be truly parallel, that is, they would not be perpendicular to the center line of the resultant structure. Such variation may be accidental or intentional. In either case, it is to be understood that such variations are to be encompassed within the scope of the present invention and that the term parallel is not to be construed in an absolute sense.

Having described the invention in connection with certain specific embodiments thereof, it is to be understood that further modifications may now suggest themselves to those skilled in the art.

What is claimed is:

1. An expandable structural module comprising a plurality of planar elements stacked in parallel relation, said elements each having a first and a second marginal edge, each element being joined along one marginal edge to the element on one side thereof and along the other marginal edge to the element on the other side thereof to form a series of folded continuous pleats, each said element having a projection on a corresponding reference plane which passes through one of the folds of said pleats, each said planar element consisting of a plurality of joined segments angularly disposed with respect to one another to enclose given angles on said reference plane and to form a generally arched configuration, said stack being expandable to unfold said pleats and encompass an increased volume within said module, thereby to move said elements out of their parallel planes, to reduce said enclosed given angles and to decrease the depth of said pleats, whereby said arched configuration is changed by decreasing the span and increasing the height of each flexible element.

2. The structural module of claim 1, wherein each of said planar elements is distorted to become non-planar as said module is expanded.

3. The structural module of claim 1, wherein each element tilts away from its initial plane as said module is incrementally expanded, thereby decreasing the depth of said pleats while increasing the volume encompassed by said structural module, each said element being distorted and becoming non-planar to change the arched configuration of said module.

4. The structural module of claim 1, wherein each said element consists of an infinite number of said segments, whereby said element forms a curved arch.

5. The structural module of claim 4, wherein radial lines from a fixed axis to two fixed points on the projection on said reference plane of said curved arch defines a first angle, and expansion of said module increases said first angle as the pleat depth decreases.

6. The structural module of claim 1, wherein each of said elements consists of at least two adjacent elongated segments, each segment having upper and lower parallel edges, said segments being joined end to end to form upper and lower marginal edges of said element, the projection of adjacent lower edges of said segments enclosing said given angle, whereby the projection of said lower margin is non-linear to a first degree, and expansion of said module decreases said given angle, whereby the proqection of said margin is non-linear to a second degree.

7. The structural module of claim 1, wherein said elements comprise a roof panel having first and second edges and first and second side wall panels, each side wall panel having a serrated edge joined to the surface of said roof panel near said first and second edges, respectively, said side wall panels being folded away from said roof panel to force said roof panel and said side panels into a continuous, arched pleated configuration, whereby each of said planar elements is comprised of a portion of said first side wall panel, a portion of said roof panel, and a portion of said second side wall panel.

8. The structural module of claim 7, further including at least one end wall panel, said end wall panel being folded to form a pleated stacked structure and being notched along one edge, whereby said edge forms a straight line for connection to the end of said roof panel when said end wall panel is expanded.

9. A foldable structural unit comprising, when folded, a plurality of planar elements stacked in parallel relation, each said element having inside and outside marginal edges, each element being joined along one marginal edge to the element on one side thereof and along the other marginal edge to the element on the other side thereof to form a series of continuous pleats, with each inside edge comprising the valley portion of a pleat and forming an arch having a first span and each outside edge forming the ridge portion of a pleat, said stack of pleated elements being expandable to enclose an increased volume within said elements, thereby decreasing the depth of said pleats, increasing the height of each said arch, and decreasing the span of each said arch, to form a three-dimensional pleated enclosure, with the valleys and ridges of said pleats being continuous along each said arch.

10. The structural unit of claim 9, wherein each said element is composed of at least two linear segments angularly disposed one to the other whereby the inside marginal edge of said element forms an arch.

11. The structural unit of claim 9, wherein each said element is composed of an infinite number of infinitesimal linear segments angularly disposed one to the other to form an arch, whereby said inside marginal edge is continuously curved.

12. The structural unit of claim 9, wherein each marginal edge of each element is retained in a plane that moves with its corresponding edge, said planes moving apart as said structural unit is expanded.

10 13. The structural unit of claim 12, wherein said planes are retained in parallel relationship as said structural unit is expanded.

References Cited UNITED STATES PATENTS 1,247,511 1 1/ 1917 Dickelman 52-90 2,534,123 12/ 1950 Hasselhorn 29454 2,667,884 2/1954 Bruno et a1. 135l9.5

FOREIGN PATENTS 214,576 7/ 195 6 Australia.

653,204 11/ 1962 Canada. 1,162,042 1/1964 Germany.

607,547 8/ 1960 Italy.

HENRY C. SUTHERLAND, Primary Examiner.

U.S. C1. X.R. 

